As an internet marketer, I always observe for the trend of niche market every time. It seems that health is the most topics that people target in internet marketing. There are lots of things related to health that really marketable and indeed, they have a pretty good sales too. There are topics that related to health like diet, medical treatments and also insurance.
Another best selling item is best anti wrinkle cream, because people basically are afraid to get old and this is a good market.